The baculovirus expression vector system (BEV) is used to produce high levels of recombinant proteins in insect cells. It is generally based on the deletion of the baculovirus polyhedrin gene (polh), which is replaced by the gene to be expressed under the control of the polh promoter. Incorporation of a bacterial origin of replication, an antibiotic resistance gene and an acceptor Tn7 recombination site into the baculovirus genome (i.e.: bacmid) has greatly improved this system, making it much faster to generate recombinant viruses (Luckow et al., 1993). Most commercially available baculovirus vectors lack the polh gene and otherwise have a complete genome, although Oxford ExpressionbTechnologies company distribute, with flashBACGOLD, a baculovirus vector negative for chitinase and cathepsin genes. It was thus anticipated that this expression system could be improved. Deletion of the chitinase and cathepsin genes from the AcMNPV genome has been shown to have a positive effect on intracellular and secreted recombinant protein stability (Kaba et al., 2004). It has also been shown that a BEV deficient in chitinase, cathepsin, p26, p10 and p74 allowed production of higher levels of recombinant proteins than those obtained with non-deletion viruses (Hitchman et al., 2009). However, expression data obtained in this latter study concerned only single recombinant proteins. For the production of complex structures such as viral vectors and virus-like particles, it is necessary to produce one or a number of proteins and, in the case of viral vectors, also a viral genome. From the results of Hitchman et al., it was not evident that the production of such complex structures could be improved in terms of protein quality when the chitinase, cathepsin, p26, p10 and p74 genes are deleted.
The aim of the present study was to provide an optimized baculovirus expression system for the production of virus vectors and/or virus-like particles.